Jonathan Kelly was last seen near to Stanley Park on May 26 and police are now appealing for information to track the missing man down.
The 51-year-old is described by police as 5'10 tall, of fat build, short fair hair, ruddy complexion. He was last seen wearing a yellow t shirt, black jeans and black shoes.
A spokesman for the police said: "Police are very worried about Jonathan. If anyone has seen him or has any information can you please contact Lancashire Police."
Anyone with information can contact police on 101 quoting log LC-20170526-2042.